Hardness versus structure in W-Si-N sputtered coatings

In this research work the influence of the addition of Si on the structure, morphology and hardness of W-(N) coatings was studied. The films were depo sited by reactive sputtering from a W target superimposed with increasing n umber of Si small plates. The partial pressure ratio between nitrogen and a rgon was varied in the range 0-2. Thus, nitrogen content was in the range 0 -60 at.%, and the silicon-to-tungsten contents ratio reached, for the great est number of silicon plates, 0.5. Depending on the nitrogen content, the structure of the films varies from t he single b.c.c. tungsten phase to the f.c.c. NaCl-type W2N. The synergistic action of both Si and N can originate the formation of amor phous structures. The hardness of the films was determined by ultramicroind entation technique by using either low loads (70 mN) and/or an empirical mo del which allows to eliminate the influence of the substrate on the measure d values. Hardness values as high as 50 GPa was obtained. Generally, the fi lms containing amorphous phases present lower hardness values than crystall ine ones. (C) 1999 Elsevier Science S.A. All rights reserved.